A case way back in 2007 by a US VoIP over broadband provider SunPocket suddenly going down without any notice that resulted in total communications blackout to over 200,000 subscribers has resulted in a ruling by the US FCC that all service providers give reasonable notice of a service interruption to prevent such problems in the future. One problem though, the breakdown of something somewhere down the line of internet access is quite broad and can be hard to diagnose and the internet being quite dynamic, it can in theory adapt, being a networked network of networks, bridges and links can be formed in split-seconds making such failures unnoticeable to most users.
This issue comes down to one of the main criticism the advent of VoIP has been nagged with since somebody discovered that you could do telephony services over the same line you use for internet access, reliability. Any issue in the links would be quite easy to resolve as they surely have happened without us even noticing a flicker in our access. One of the biggest problems is when a major hub or interchange between the networks or say one of the major backbones that links a whole section of the world gets damaged by nature or man (a recent cable dug up in the Middle East caused days of no access for Asia and many other countries).
VoIP is the next step but a more robust framework must be established to allow it to function, say in the next predicted solar storm that can disrupt power, communications and everything else that uses electricity if we were caught off-guard. Time is coming when VoIP will replace the humble telephone which has served us for many a years, if we could just make it as bullet proof or even nearly as bulletproof as standard telephony then maybe the world would fully embrace it.